Motor



Feb. 6, 1934.

R. COFFMAN MOTOR Filed Aug. 28, 1929 3 Sheets-Sheet 1 NM 3 N w E m .mw m

v L 2:12;: m N E @WNND Feb. 6, 1934. R, A, COFFMAN 1,946,309

MOTOR Filed Aug. 28, 1929 3 Sheets-Sheet 2 INVENTOR MMA CWl/k ,W a r a! R. A. COFFMAN 1,946,309

MOTOR Filed Aug. 28, 1929 3 Sheets-Sheet 3 .1/ mm A INVENTOR M A WW) )3? W W, WM,

Patented Feb. 6, 1934 UNITED STATES PATENT OFFICE MOTOR Roscoe Coflman, Pittsburgh, Pa. Application August 28, 1929. Serial No. 388,870

18 Claims. (01. 121-37) The present invention relates broadly to motive devices, and more particularly to an improved motor construction such as is especially adaptable for use as a starting motor for internal combustion engines, and especially engines of such type as utilized in aviation work.

In the provision of a starting motor of the character above referred to, it is essential that the motor be capable of developing the necessary torque for turning over the engine quickly and efliciently, and that the parts of the motor shall I be extremely light and compact. v

The present invention relates to a motor satisfying the requirements in the respects referred to, and adapted further to cooperate therewith in such manner as to effectively serve as a scavenging means for certain parts of the engine structure.

The present invention further provides a unit structure including a motor of the fluid pressure operated type in combination with a source of fluid pressure supply, the entire unit being of such compact construction as to facilitate its bodily attachment to or removal from an engine or other device to be driven thereby.

In the accompanying drawings I have show for purposes of illustration only, certain preferred embodiments of the present invention.

In the drawings:

Figure 1 is a longitudinal sectional view through a motor constructed in accordance with the present invention;

Figure 2 is a transverse sectional view on the line 11-11 of Figure 1, illustrating the cooperative relationship between the motor and a source of fluid pressure;

Figure 3 is a transverse sectional view on the line IIIIII of Figure 1, looking in the direction of the arrows, and illustrating the cooperative relationship between the driving and driven members;

Figure 4 is a transverse sectional view on the line IV-IV of Figure 1, looking in the direction of the arrows;

Figure 5 is a view partly in side elevation and partly broken away for the purpose of illustrating the construction of the driving member; and

Figure 6 is an enlarged longitudinal sectional view of the exhaust valve and associated portions of the driving means and casing, the valve being shown in open position. i

In view of the requirements as to compactness with devices of the general character to which the present invention relates, it is not feasible to provide a construction in which a great movement in a direction generally axially of the device is required for the reason that such a movement requires a casing of such length as to exclude the successful use of the motor.

The present invention, therefore, contemplates a motor including driving and driven members of such construction as to have a combined relative rotatable movement therebetween and longitudinal movement, the construction of the parts being such that the rotative effect transmitted 5 by the driving member to the driven member is multiplied so that a considerable amount of rotation for a relatively short longitudinal movement is secured. This makes it possible to utilize a casing of small overall dimensions.

In carrying out the present invention there may be provided a housing 1, of substantially cylindrical shape, having at one end thereof a flange 2, adapted for cooperation with an engine or other device in connection with which the'75 motor is to be utilized. This flange may be provided with any desired number and arrangement of openings 3 extending therethrough for the reception of bolts or other fastening means. In view of the requirements in a device of this 30 character for lightness of construction, the housing 1 is conveniently formed of aluminum or similar material. In order to effectively reinforce this material to the extent required, so that it may. successfully withstand any tendency toward relative rotative movement between the same and its associated engine, the openings 3 suitable clamping ring 9.

Extending through the respective flanges 5 and 7 on the housing and sleeve, are bushings 10, of a construction generally similar to that of the bushings before described, but serving in addition to the function of tying together the respective flanges against relative rotation, the further function of providing exhaust ports from the interior of the cylinder for the purpose hereinafter more fully set forth. The sleeve 8 as herein illustrated projects in opposite directions from the plane of the flange '7, and is provided on its inner surface with pressure.

threads or splines 11, having a pitch determined by the duty to he performed by the motor.

Cooperating with the splines 11 is a driving member 12, herein illustrated as being of generally cylindrical shape, and having on its exterior surface, threads or splines 13, of the same constructional characteristic as those of the splines 11, and adapted for interengagement therewith. This interengagement is such that upon reciprocation of the driving member 12, to the left, as viewed in Figure 1 of the drawings, it will have imparted thereto a rotative movement about the axis aa of the motor.

For effecting the desired reciprocating movement of the driving member, there may be provided a piston 14, having suitable packing 15, for cooperation with the walls of the cylinder 6 and of such dimensions and type as to cooperate therewith with a minimum of clearance.

Cooperating with the cylinder 6 is a connection 16, by means of which fluid under pressure from any desired source and of any desired characteristics may be delivered into the cylinder for effecting movement of the piston in one direction. While ordinarily devices of this character are operated by means of compressed air, the present invention provides a construction which is adaptable for use either with such a motive fluid, or with liquefied gases, such as carbon dioxide, or by means of oil or water under It will be understood that the utility of the invention is not limited with respect to the characteristics or source of the motive fluid utilized.

In order to provide a light construction, the cylinder 6 is conveniently of material having characteristics similar to that of the housing 1, and the piston 14 is of similar material. In order to permit such a construction and at the same time insure a tight sliding fit between the piston and cylinder, the skirt 1'? of the piston is conveniently formed of considerably smaller diameter than the internal diameter of the cylinder to provide ashoulder 18 for cooperation with the packing 15 clamped between such shoulder and a similar shoulder 20 on a bearing and clamping ring 21. This ring has its outer surface machined to slightly smaller diameter than the internal diameter of the cylinder and shaped to receive a hardened bearing insert 22 therearound providing the sliding engagement and wear surface between the piston and cylinder, and permitting the use of relatively soft light metals in both cylinder and piston.

In addition to the threads or splines 13 formed on its outer surface, the driving member 12 is provided on its inner surface with similar threads or splines 23, extending, however, in the opposite direction from that of the splines 13. These splines in turn cooperate with similar threads or splines 24 on a driven member 25, mounted, in accordance with the preferred embodiment of my invention, for botn rotative and limited longitudinal movement. On its outer end, the driven member is provided with suitable clutch teeth or similar means 26, adapted for engagement with similar means 27, on the part 28, to which rotation is to be imparted. As will be apparent from Figure 1 of the drawings, the relationship of the respective means 26 and 2'7 is preferably such as to provide clearance therebetween. -In order, therefore, to effect interengagement of these means, a limited longitudinal movement is required. After such a movement to bring the means into engagement, the driven member may be rotated to effect the desired rotation of the engine or other mechanism 28 to be rotated.

For insuring such a limited longitudinal movement of the driven member 25 in advance of any material rotation thereof, it is provided on its inner surface with a series of spring arms 29 adapted to cooperate with the head 30 on the hollow rod 31 carried by the piston 14 and projecting inwardly therefrom substantially concentrically of the driving member 12.

By reason of this construction, the initial movement of the piston 14 will be effective for bringing the head 30 into engagement with the spring arms 29. The resistance of these arms will be such as to insure a longitudinal movement of the driven member 25 before they yield to an extent sufiicient to permit the passage of the head 30 therebetween. This longitudinal movement will besufficient for bringing the respective means 26 and 27 into engagement whereby the continued movement of the driving member 12 will be effective for accomplishing the desired operation. When the driven member 12 starts forward with the piston at the beginning of the working stroke it starts to rotate under the influence of the screw threads 13. It also carries the driven member 25 forwardly with it, but there is no relative rota tion between 12 and 25 at this time. They both turn together but 25 does not turn any faster than 12 until it meets the resistance occasioned when its clutch teeth 26 engage the clutch teeth 2'7; then 25 starts to turn faster than 12 because it is then turned under the influence of the two sets of screw threads.

After such operation has been accomplished, an exhaust of cylinder 6 may be made manually through the connection 16, or provision may be made for the automatic exhausting of the fluid within the cylinder 6. Where the fluid is of such nature as to have no detrimental action on the engine or other mechanism with which the motor is associated, I preferably exhaust the cylinder directly into the crank caseof such engine. Such an operation possesses the dual advantages of an automatic exhausting of the cylinder whereby a separate operation on the part of a pilot, for example, is not required for this purpose. Also, where such fluid is discharged, for example, into the crank case of an engine, it serves to scavenge such crank case from any accumulated vapors or gases therein, the entire mixture being subsequently dissipated through the usual breather connections, as will be understood by those skilled in the art.

The cylinder having been exhausted, the piston is ready for its return stroke, this conveniently being accomplished by means of a. spring 32, herein illustrated as being of such construction as to serve both as a compression spring and a torsion spring. This may be accomplished by providing the spring with an offset 33 at one end, adapted to cooperate with a suitably shaped recess 34 in the piston, and with a second offset 35 at the opposite end, adapted to interengage with a suitable recess 36 in the sleeve 8.

It will be apparent to those skilled in the art that with a construction of the character described, reciprocating movement of the piston 14, due to its rotation, will tend to wind up the spring 32 as well as compress the same. Therefore, the natural tendency of the spring to unwind and expand will be effective for producing the desired movement of the piston. As the piston approaches its normal position illustrated in Figure 1, the head 30 on the rod 31 comes into engagement with the spring arms 29, and slides therethrough into engagement with a shoulder 37 projecting inwardly from the driven member. This engagement is such that the continued retractile movement of the piston 14 serves to positively pull the driven member 25 endwise, and thereby disengages the means 26 and 27.

In order to seal the piston against continued exhaust therethrough of the fluid pressure where it is of such construction as to provide for the automatic exhausting thereof in the manner referred to, the piston may be provided with a valve 38 carried by a stem 39 projecting outwardly from a spider 40, movable within a casing .41, conveniently threaded into the driving member 12 and in turn providing the desired threaded engagement with the rod 31, as illustrated in Figure 6. Accordingly, the valve 38 and rod 31 move with the driving member 12 and piston 14. The valve 38 is preferably of a disk of hardened steel and cooperates with the seat 42 of hard metal for closing the space around the. stem 39. By reason of the heavy pressure encountered in the starter, the disk 38 andseat 42 should be given a ground finish.

The spider 40 is provided with radial arms 43 which conform to the shape of the interior of the casing 41. The arms 43 are provided with spring press pins 44, which are urged outwardly to cooperate with either of the annular grooves 45 and 46 formed in the interior ofthe casing 41. If desired, the grooves 45 and 46 may be formed in a liner 47, insertable into the casing 41. a Assuming the valve 38 to be in the closed position illustrated in Figure 1, it will remain in such position during substantially the entire operative stroke of the piston 14. At substantially the completion of the piston travel, projections 48 on the spider 40 will come into engagement with the shoulder 37 on the driven member 25 and check further travel of the valve plate with the piston.

This will be eflective for disengaging the pins 44 from the groove 45 and moving them into engagement with the groove 46, whereby the valve is held in its open position during exhaust. During exhaust, the fluid under pressure escapes betweenthe valve 38 and the seat 42, throughthe space between the seat 38 and the stem 39, and

. between the arms 43, as shown by the arrow in Figure 6.

During substantially the entire return movebringing the pins 44 into engagement with the groove 45.

Fluid in escaping through the valve 38 flows into the interior of the rod 31 and thence through the driven member to the space between the clutch means 26 and 27. This fluid in striking the part 28 will be distributed outwardly and will be effective not only for removing from such clutch means any accumulation of grease or foreign material, but will be further effective upon passing into the crank case on the engine for removing the gases therefrom, as before referred to. V

For maintaining the member 25 in proper'position within the housing, it may be provided on its outer end with a reversal turned portion 25,

cooperating with a suitable bushing 25*, which is in turn carried by the sleeve 8 and a second sleeve 51, respectively.

The sleeve 51 is provided with a shoulder 52, adapted to cooperate with a bearing ring 53 of a suitable thrust bearing, herein illustrated as being of the anti-friction type, the opposite ring 54 of which is directly carried by the housing 1. This bearing tends to take up any thrust of the sleeve 51 to the left, as viewed in Figure 1 of the drawings. The thrust in the opposite direction may be opposed by suitable bushings 55, supported by the sleeve 8, adjacent the flange 7 formed thereon.

Projecting inwardly from the outer end of the sleeve 51 is one or more slots 56 adapted to engage suitable projections 57 on the part 28. This construction is such that even after the respective clutch means 26 and 27 have been disengaged in the manner before referred to, the projections 57 will remain in driving engagement with the slots 56 for thereby rotating the sleeve 51. Advantage may be taken of such rotation for producing a continuous supply of fluid under pressure by providing the sleeve with a gear 58, adapted to drive a gear 59, on theshaft 60 of a suitable compressor carried by the housing 1. This compressor may be of any desired construction, as well understood in the art, and its constructional characteristics other than those required to cause it to form a unit with the motor do not constitute any part of the present invention. This provides a unitary construction including a motor and compressor whereby the motor may be utilized as a starting means for the engine, the engine utilized after it has been started as a driving means for the compressor, and the compressor utilized for supplying fluid to the motor.

From the foregoing description it will'be apparent to those skilled in the art that during reciprocation of the driving member 12, it not only imparts to the driven member 25 its own rotation as determined by the cooperation between the splines 11 and 13, but also an additional rotation as determined by the cooperation of the splines 23 and 24. In other words, the actual rotation of the driven member is amplified by the mechanism provided so that only half as long a stroke of the driven member is required as would be required if a single threaded construction were utilized.

. This makes it possible to considerably shorten the overall dimension of the motor, as will be readily apparent, and better adapts it for the performance of the various duties for which it is designed. It likewise serves to conserve the quantity of operating fluid required for each op-. eration, this being particularly desirable in case the operation is obtained by the use, for example, of individual cartridges or containers of liquid CO: or the like. a

It is likewise desirable when compressed air is utilized, inasmuch as the dimensions of the container may be made correspondingly smaller and therefore lighter than would be possible if greater capacity were required.

The relatively short and compact structure provided by the intemesting or telescoping of the parts 8, 12, and 25 enables me to locate all of these parts wholly upon that side of the piston 14, remote from the working face of the piston. In other words, these parts which carry the operating splines are never exposed in the pressure chamber oi the cylinder and consequently are never contacted by the gases of propulsion which might attack said splines or interfere with the highly essential lubrication thereof. Further, since no threads or splines extend through the piston, there is no leakage of the pressure fluid along said splines.

The present invention possesses the further advantage of effecting the desired starting of an in ernal combustion engine, for example, without subjecting the same to a sudden shock, such as is produced in starters of the types ordinarily utilized. This not only materially increases the length of life of the motor parts, but also of the engine parts, and again is of advantage,particularly in aeroplane work, in that it enables all of such parts to be designed accordingly with a corresponding saving in weight.

The use of carbon dioxide either in individual containers of such capacity as to effect a single operation of the motor, or from larger containers, or directly from a compressor of the character hereinbefore referred to, possesses a peculiar advantage in a starting motor, and particularly where such starting motor is utilized for the starting of an aeroplane engine. This is due to the fact that CO: is not only non-combustible, but is actually a good extinguisher of flame. The exhausting of an atmosphere of CO2 in proximity to an engine at the time of starting and at the time when it is more susceptible to back-firing than under normal conditions of operation is decidedly advantageous, whether such exhaust occur-through the crank case, or merely in the general atmosphere adjacent to the engine. Such a discharge of CO2 not only serves to produce a temporary blanket of non-combustible characteristics, but also serves to carry away any combustible vapors which may have formed during periods of rest of the engine.

While I have herein disclosed certain preferred embodiments of my invention, it will be apparent to those skilled in the art that changes in the construction and arrangement of the parts may be made without departing either from the spirit of my invention, or the scope of the appended claims.

1. In a motor, rotatable driven means, reciprocating driving means, means for rotating said driving means upon reciprocation thereof, and interengaging means between the driving and driven means for rotating said driven means upon such reciprocation, said two last mentioned means being effective for impartingto the driven means a greater rotation than that of the driving means and a piston for imparting movement to the driving means, both of said rotating means lying wholly upon that side of the piston remote from its working face in all positions of piston travel.

2. In a motor, a rotatable driven member, a reciprocating driving member, means for rotating said driving member upon reciprocation thereof, interengaging means between the driven and driving members for rotating said driven member upon such reciprocation, said means be ing effective for imparting to the driven member a greater rotation than that oi the driving member, and separate means for effecting reciprocation of said driving member in opposite directions including a piston, both of said rotating means lying wholly upon that side of the piston remote from the working face of the piston throughout all positions of piston travel.

3. In a motor, a rotatable driven member, a reciprocating driving member, means for rotating said driving member upon reciprocation thereof, and interengaging means between the driven and driving members for rotating said driven member upon such reciprocation, said means including splines effective for imparting to the driven member a greater rotation than that of the driving member and a piston for imparting movement to the driving means, all of said splines lying wholly upon that side of the piston remote from the working face of said piston, throughout all positions of piston travel.

4. In a motor, a rotatable driven member, a reciprocating driving member telescopically mounted relatively to the driven member, means for rotating said driving member upon reciprocation thereof, and interengaging means between the driving and driven members for rotating said driven member upon such reciprocation, said means including splines effective for imparting to the driven member a greater rotation than that of the driving member, means for reciprocating the driving member comprising a pressure receiving cylinder and a piston therein carried by said driving member, both the driving and driven members and all of the means for rotating the same being disposed upon that side of the piston remote from its working face throughout all positions of piston travel.

5. In a motor, rotatable driven means, reciprocating driving means, means for rotating said driving means upon reciprocation thereof, interengaging means between the driving and driven means for rotating said driven means upon such reciprocation, and means for causing said driven means to have limited longitudinal movement prior to the rotational movement thereof, a clutch element upon the driven means, a piston carried by the driving means, and a cylinder within which the piston travels and which provides a pressure chamber for the piston, all parts of the driving and driven means and the means for rotating the same being completely separated from said pressure chamber by the piston throughout all positions of piston travel.

6. In a motor, rotatable driven means, reciprocating driving means, means for rotating said driving means upon reciprocation thereof, interengaging means between the driving and driven means for rotating said driven means upon such reciprocation, and yieldable means for causing said driven means to have limited longitudinal movement prior to the rotational movement thereof, a clutch element upon the driven means, a piston carried by the driving means, and a cylinder within which the piston travels and which provides a pressure chamber for the piston, all parts of the driving and driven means and the means for rotating the same being completely separated from said pressure chamber by the piston throughout all positions of piston travel.

7. In a motor, rotatable driven means, reciprocating driving means, means for rotating said driving means upon reciprocation thereof, interengaging means between the driving and driven means for rotating said driven means upon such reciprocation, and means including a resilient member carried by one of said means and frictionally engaging the other of said means for producing limited longitudinal movement of the driven member at substantially the commencement of rotation.

8. In a motor, rotatable driven means, reciprocating driving means, means for rotating said driving means upon reciprocation thereoi.','interengaging means between the driving and driven means for rotating said driven means upon such reciprocation, and means including a resilient member disposed in one of said means and yieldably engaging the other of said means for producing limited longitudinal movement of the driven member at substantially the commence ment of rotation.

9. In a motor, rotatable driven means, reciprocating driving means, means for rotating said driving means upon reciprocation thereof, interengaging means between the driving and driven means for rotating said driven means upon such reciprocation, and means including a resilient member disposed in the driven means and means carried by the driving means and having sliding frictional engagement with the resilient member for producing limited longitudinal movement of the driven member at substantially the commencement of rotation.

10. In a motor, rotatable driven means, reciprocating driving means, means for rotating said driving means upon reciprocation thereof, interengaging means between the driving and driven means for rotating said driven means upon such reciprocation. and means including a resilient member carried by one of said means and a cooperating member carried by the other means and frictionally engaged with said resilient member for producing limited longitudinal movement of the driven member at substantially the commencement of rotation.

11. In a motor, a rotatable driven member, a reciprocating driving member, fluid pressure means for eifecting movement of said driving member in one direction, other means for effecting movement of said driving member in the opposite direction, means for rotating said driving member upon reciprocation thereof, means for imparting limited longitudinal movement to the driven member at substantially the beginning of reciprocable movement, and interengaging means for rotating said driven member upon said reciprocation, said last mentioned means including splines effective for imparting to the driven member a greater rotation than that of the driving member, a, clutch element upon the driven means, a piston carried by the driving means, and a cylinder within which the piston travels and which provides a pressure chamber for the piston, all parts of the driving and driven means and the means for rotating the same being completely separated from said pressure chamber by the piston throughout all positions of piston travel.

12. A motor comprising a rotative driven element, a fixed element, a driving element telescopically disposed internally with respect to one of said elements and telescopically disposed externally with respect to the other of said elements, means for thrusting said driving element longitudinally with respect to said .rotative and fixed elements, and interengaging members upon said elements for imparting rotation to the driving element from the fixed element and for imparting rotation to the driven element from the driving element under the influence of such longitudinal movement of said driving element.

13. A motor comprising a rotative driven element, at fixed element, a driving element telescopically disposed internally with respect to the fixed element and telescopically disposed externally with respect to the driven element, means for thrusting said driving element longitudinally with respect to said rotative and fixed elements, and interengaging members upon said elements for imparting rotation to the driving element from the fixed element and for imparting rotation to the driven element from the driving element under the influence of such longitudinal movement of said driving element.

14. A structure as recited in claim 12 comprising yieldably engaging means between the driving element and the driven element for imparting limited longitudinal movement to the driven element prior to the maximum rotation of said element under the influence of the reciprocation of the driving means.

15. A structure as recited'in claim 12 compris ing a piston as the means for thrusting the driving element longitudinally, and friction means carried by the piston for engaging the driven element for imparting limited longitudinal movement to the driven element prior to the maximum rotation of said element under the influence of the reciprocation of the driving means.

16. A structure as recited in claim 12 wherein the means for thrusting the driving element longitudinally comprises a cylinder, a piston by which the driving element is carried, movable in said cylinder, and an exhaust valve actuated by the movement of said piston and controlling the passage of exhaust fluid through the piston.

17. A structure as recited in claim 12 wherein said driving and driven elements are of tubular formation and wherein the means for thrusting the driving element longitudinally comprises a piston, and an exhaust valve carried by said piston and arranged to discharge the exhaust through the tubular driving and driven elements.

18. A structure as recited in claim 12 in combination with an air compressor driving element telescopically disposed with respect to the driven element, an engine crank shaft carried part, and means for driving the compressor driving element from said part.

ROSCOE A. COFFMAN. 

